Pumps for pumping molten metal are known and include various components depending on the application and the manufacturer, including circulation, transfer and gas purification pumps. A gas purification pump disclosed in U.S. Pat. No. 5,993,728 to Vild, is used for injecting chlorine gas into molten metal to react with magnesium such as from aluminum can scrap. The pump includes a submerged base having an interior impeller chamber having an inlet opening. A discharge passageway leads from the impeller chamber to an exterior of the pump. An impeller is rotated in the impeller chamber, which draws molten metal through the inlet into the impeller chamber and out the discharge passageway. The chlorine gas is injected into the discharge passageway. Chlorine gas is extremely toxic and may enter the surrounding area creating a hazardous workplace.
In conventional practice as shown by U.S. Pat. No. 4,052,199 to Vild, solid flux can be manually added to another chamber downstream of the pump. This practice is dangerous because the operator must be very near the molten metal when adding the flux. This is added to the molten metal in the case of aluminum can scrap to remove magnesium, which is present in aluminum cans in substantial amounts.
U.S. Pat. No. 6,589,313 discloses a hollow shaft on the end of which is an impeller. The shaft and impeller are rotated and positioned at an angle relative to the bath by a complex apparatus. Solid flux and gas is added to the rotating shaft and dispersed in the molten metal.